Effect of growth rate on microstructure and tensile properties of Ti-45Al-2Cr-2Nb prepared by electromagnetic cold crucible directional solidification

摘要

Ti-45Al-2Cr-2Nb alloy was directionally solidified at different growth rates varying from 02 to 12 mm/min by applying an electromagnetic cold crucible directional solidification technique. It was determined that well-aligned α_2 (Ti_3Al)/γ(TiAl) lamellar structures, B_2 phase and blocky γ phase were generated in columnar grains. The interlamellar spacing (λ) decreases with the increasing growth rate (Ⅴ) according to the relationship λ ∝ V~(-0.48), but the volume fraction of B_2 is increased as growth rate is increasing. Results of uniaxial tensile tests show that the B_2 phase and the blocky γ phase have significant influence on tensile failure when they are presented in the matrix of α_2/γ lamellar structures, because they are usually employed to act as cracking sources during the tension process.